1. Filed of the Invention
This invention generally relates to a control apparatus and method for operating an electromagnetic valve. More particularly, the present invention pertains to a control apparatus and method for opening and closing an electromagnetic valve body functioning as an intake valve and exhaust valve of internal combustion based on an electromagnetic force of an electromagnet.
2. Description of Related Art
Known control apparatuses of electromagnetic valve for controlling valve bodies functioning as intake valves and exhaust valves of internal combustions based on the electromagnetic force of electromagnet have been disclosed. In the known control apparatuses of electromagnetic valves, because the external force based on the internal pressure of a combustion chamber (i.e., cylinder pressure) and the intake or exhaust pressure affect the valve body in addition to the electromagnetic force of the electromagnet, it is required to consider the influence of the external force when actuating the valve body. For example, when opening the valve body and when the large vacuum pressure is generated in the combustion chamber, the valve body is attracted in the direction for opening the valve by the vacuum. Accordingly, the displacement speed of the valve body may become unnecessarily large when reaching the fully open position. In this case, the valve body which is once reached the fully open position may rebound to the closing side, which reduces the operational stability. In addition, the valve body may be attracted in the direction for closing the valve due to the external force based on the cylinder pressure and the intake and exhaust pressure when closing the valve body. In this case, the operational stability is also reduced due to the rebound of the valve body.
A known device disclosed in a Japanese Patent Laid-Open Publication No. 2000-130198 generates the electromagnetic force for attracting the valve body towards the valve closing side when it is assumed that the vacuum pressure generated in the combustion chamber increases, such as when fuel injection is halted, so that the electromagnetic force counterbalances the external force for attracting the valve body in the direction for opening the valve.
Meanwhile, the external force affecting the valve body is not constant but is varied in accordance with the condition of the cylinder pressure and the intake and exhaust pressure, that is, in accordance with the engine operation. Accordingly, in the foregoing known device, the period for generating the electromagnetic force for attracting the valve body in the direction of closing the valve is predetermined in accordance with the engine operation in order to generate the electromagnetic force appropriate for the engine operation condition in the electromagnet.
However, in order to generate the electromagnetic force appropriate for the engine operation condition in the electromagnet, it is required to devise a countermeasure such as predetermining the aforementioned period for generating the electromagnetic force commensurate with the engine operation condition. That is, it is required to obtain the relationship between the engine operation condition and the appropriate electromagnetic force in advance through experiments and to memorize the results as a control map. This approach requires a long time for establishing and adjusting the necessary control constants.
Accordingly, the present invention is provided considering the aforementioned drawbacks. The present invention provides a control apparatus and method for an electromagnetic valve for actuating the valve body with appropriate electromagnetic force in accordance with the engine operation and for simplifying the determination of control constants used for the electromagnetic valve control.